JPS63204521A - Tilt servo device - Google Patents

Abstract

PURPOSE:To reduce the residual error of a tilt and to reduce also crosstalk by executing tilt servo in a lead-in area at the time of reproducing a CD area and over the whole servo effective area at the time of reproducing a video area in the case of reproducing a composite disk. CONSTITUTION:When a slider base 15 is moved from a position (a) to a position (b) and reached an inclined part on the outer peripheral part of a disk 1, a tilt mechanism 17 is driven in accordance with a driving signal outputted from a tilt servo device 7 based on an output from a tilt sensor. An optical system body 14 is rotated around a rotating supporting point 16 in the clockwise direction and the mechanism 17 is stopped at its operation on a position where an optical axis A-A' is rectangular to the information recording face of the disk 1. The tilt servo device changes timing for servo operation in accordance with reproducing areas (a CD area and a video area) and the servo operation is controlled by a system controller 9. Consequently, a residual error of a tilt can be reduced in both CD and video areas and crosstalk can be also reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a tilt servo device in an optical information recording disk reproducing device.

BACKGROUND ART In information recording disc playback devices such as video disc players and digital audio disc players, recorded information on an information recording disc (hereinafter simply referred to as a disc) is read using a light beam emitted from an optical pickup. If the disc is warped, the information recording surface of the disc will be tilted with respect to the optical axis of the information detection optical beam (hereinafter referred to as the main beam), making the track pitch with the adjacent recording track equivalent. Therefore, if the beam spot diameter on the information recording surface is kept constant, it will be more susceptible to the influence of bit information of adjacent recording tracks, leading to an increase in crosstalk.

In order to improve such performance deterioration, a tilt servo light beam (hereinafter referred to as tilt beam) is irradiated onto the information recording surface of the disk, and the optical axis of the main beam is aligned with the information recording surface based on the reflected light. A tilt servo device is used to control the tilt of the pickup so that it is always at right angles to the pickup.

In actual disc playback, in the case of video discs, tilt servo is performed to the outer periphery of the disc to the extent that the tilt beam spot does not extend beyond the disc outer diameter.
In the case of digital audio discs, tilt servo is performed only in the lead-in area because the material is less likely to warp and the error rate will not deteriorate significantly even if some residual tilt error exists.

By the way, it has the same dimensions as a digital audio disk called a compact ◆ disk, and as shown in FIG.
A first area (hereinafter referred to as CD area) 1a on the inner side where the frequency modulation processed video signal and PCM audio signal are multiplex recorded. The second area (hereinafter referred to as
Discs (hereinafter referred to as composite discs) on which information is recorded are being developed in which areas are divided into a video area (1b) and 1b (referred to as a video area).

When considering playback of such a composite disc, the inner CD
Regarding the area, it can be dealt with by applying tilt servo only in the lead-in area, but if the information recording surface is slightly tilted with respect to the optical axis of the main beam on the inner periphery, the residual error will increase as you go to the outer periphery. So,
In the video area located on the outer circumferential side, crosstalk may worsen due to angular errors, and countermeasures are desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a tilt servo device that can reduce residual tilt errors and reduce crosstalk in both the CD area and the video area when playing a composite disc. purpose.

The tilt servo device according to the present invention is configured to perform tilt servo only in the lead-in area when reproducing a CD area and over the entire servo effective range when reproducing a video area when reproducing a composite disc.

Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an example of an optical information recording disc reproducing apparatus equipped with a tilt servo device according to the present invention. In the figure, a disk 1 is rotationally driven by a spindle motor 2, and recorded information is read by an optical pickup 3. This pickup 3
The optical system includes a laser diode as a light source, an optical system including an objective lens, a 4-split photodetector that receives reflected light from the disc 1, and further controls the position of the objective lens in the optical axis direction with respect to the information recording surface of the disc 1. A focus actuator, a tracking actuator that controls the position of the main beam spot emitted from the pickup 3 in the disk radial direction with respect to the recording track, a tilt servo mechanism and a tilt sensor, which will be described later, are built in. The read output of the pickup is supplied via an RF (high frequency) amplifier 4 to a video information demodulation system 5 and a digital information demodulation system 6, and the output of the tilt sensor is supplied directly to a tilt servo device 7. This tilt servo device 7 will be explained in detail later.

In the video information demodulation system 5 , the reproduced RF signal from the RF amplifier 4 is demodulated into a video signal by a video demodulation circuit 50 and then supplied to a time axis correction circuit 51 . The time axis correction circuit 51 is composed of, for example, a variable delay element such as a CCD, and is configured to perform time axis correction by changing the amount of delay of the element in accordance with a control signal from the time axis control circuit 52. . The time axis control circuit 52 outputs the oscillation output of a crystal oscillator (VCXO) 54 that oscillates in synchronization with the horizontal synchronization signal separated from the video signal by the synchronization separation circuit 53 and its frequency-divided output, and the time axis correction circuit 51. The structure is such that a control signal is generated in accordance with the phase difference between the horizontal synchronization signal and the color burst signal in the video signal passed through the video signal. The video signal subjected to time axis correction by the time axis correction circuit 51 is supplied to the video output terminal 8 via the video signal processing circuit 55. The video signal processing circuit 55 performs various processes such as video muting for inhibiting the output of video signals and character insertion.

On the other hand, the digital information demodulation system 6 is provided with a changeover switch 60 that is switched depending on the area to be played back (CD area and video area) when playing back a composite disc. When the video area is played back, it is on the b side, and the switching is performed in response to a switching command issued from the system controller 9, which will be described later. The PCM audio signal recorded in the CD area and the video area is, for example, E F M (Eight
t t.

During reproduction of the CD area, the reproduced EFM signal passes through an equalizer circuit 61 and an amplifier 62, and then is supplied to a demodulation/correction circuit 66 via a changeover switch 60. On the other hand, when reproducing the video area, the EFM extraction circuit 63
The reproduced EFM signal extracted by passes through an equalizer circuit 64 and an amplifier 65, and then is demodulated via a changeover switch 60◆
The signal is supplied to a correction circuit 66.

The demodulation/correction circuit 66 demodulates the EFM signal into R
In addition to writing to a memory such as AM (not shown), data is written to a RAM based on the reference clock from the reference clock generator 67.
control, exchange data, de-interleave, and perform error correction using the parity contained in the data. The digital audio signal demodulated and corrected by the demodulation/correction circuit 66 is processed by the audio signal processing circuit 68, which includes a D/A (digital/analog) converter, a deglitcher, etc., and then output as audio outputs for left and right channels. Terminal 10L, IO
Supplied to R.

A position detector 11 is provided near the movement path of the pickup 3 in the disk radial direction, and detects the movement position of the main beam spot emitted from the pickup 3 in the disk radial direction. The obtained position information is supplied to the system controller 9. Based on this position information, it is possible to detect that the main beam spot has arrived near the boundary between the CD area and the video area. System controller 9
consists of a microcomputer, which exchanges data with each section such as the video information demodulation system 5 and the digital information demodulation system 6 via the path line 12, and provides switching commands to the changeover switch 60 in the digital information demodulation system 6. It also generates servo on/off commands to the tilt servo device 7, etc.

FIG. 2 is a configuration diagram showing an example of a tilt servo mechanism built into the pickup 3. In the figure, reference numeral 13 denotes an objective lens constituting a part of the pickup 3, which is attached to the optical system body 14 so as to be movable in the optical axis direction, and is driven in the optical axis direction by a focus actuator (not shown). The optical system body 14 is attached to the slider base 15 so as to be freely rotatable about a rotation fulcrum 16 located on the optical axis AA' of the objective lens 13. Reference numeral 17 denotes a tilt mechanism composed of a motor M (shown in FIG. 3), a speed reduction mechanism, etc., which moves the optical system body 14 to the slider base according to a drive signal supplied from the tilt servo device 7 (shown in FIG. 1). By rotating the objective lens 13 with respect to the information recording surface, the inclination of the optical axis AA' of the objective lens 13 with respect to the information recording surface is adjusted. The slider base 15 is movable in the radial direction BB' of the disk 1 along a guide rail (not shown), and is driven by a drive mechanism (not shown) comprising, for example, a slider motor, a reduction gear, or the like.

A tilt sensor 18 (a tilt sensor 18 for detecting the inclination angle of the disk 1 with respect to the optical axis AA') is located in the center that includes the optical axis AA' of the objective lens 13 and is perpendicular to the moving direction of the slider base 15. 3) is provided close to the objective lens 13. As shown in FIG. 3, this tilt sensor 18 includes one light emitting element 19 and two light receiving elements 2.
The light receiving elements 20a and 20b receive the reflected light from the information recording surface of the disk 1 based on the light beam emitted from the light emitting element 19, and supply the received light output to the tilt servo device 7. The beam spot on the information recording surface by the tilt sensor 18 is located on the slider base 1.
It is spaced apart from the main beam spot by a predetermined distance #d in a direction perpendicular to the moving direction of the main beam spot. In the tilt servo device 7, the difference between the amounts of light received by the two light receiving elements 20a and 20b is obtained by a differential amplifier 70, and this difference signal is used as the amount of tilt of the disc 1 with respect to the optical axis A-A' and is driven via a servo switch 71. The signal is supplied to a circuit 72 and used as a drive signal for the motor 21 in the tilt mechanism 7 (shown in FIG. 2). The servo switch 71 is controlled on/off by the system controller 9 (shown in FIG. 1).

In this configuration, when the slider base 15 moves from position (a) to position (b) in FIG. The tilt mechanism 17 is activated in response to the drive signal, and the optical system body 14 is rotated clockwise in the figure around the rotation fulcrum 16, so that the optical axis A-
The tilt mechanism 17 stops operating at the position where A' is perpendicular to the information recording surface of the disc 1.

The tilt servo device 7 applies servo at different times depending on the area to be reproduced (CD area and video area), and is controlled by the system controller 9. That is, the system controller 9 can determine the playback area based on the position information from the position detector 11, and in the CD area, the servo is effective only in the lead-in area, and in the video area, the servo is effective, which is determined by the distance d between the tilt beam spot and the main beam spot. The servo switch 71 is turned on to perform servo over the entire range.

Regarding the CD area, this area is located on the inner circumferential side of the disc, and even if there is a residual tilt error, the error rate does not deteriorate that much, and the program contents of each area recorded in the lead-in area and absolute TOC indicating time etc.
It is sufficient if the (Table Of' Contents) information can be detected accurately. On the other hand, regarding the video area on the outer periphery, as mentioned earlier, if the information recording surface is slightly tilted with respect to the optical axis of the main beam on the inner periphery, the residual error will increase as you go to the outer periphery, and due to the angular error. Since crosstalk may worsen, it is preferable to perform tilt servo over the entire video area. However, as shown in FIG. 4, the tilt beam spot on the information recording surface is separated from the main beam spot by a predetermined distance fid in a direction perpendicular to its moving direction, and the main beam reaches the outer edge of the disk. Since the tilt beam spot is already outside the disk, it is impossible to perform tilt servo over the entire video area, and the effective range a in which servo can be performed is determined by the above-mentioned separation distance d.

This servo a effective range S is determined as follows.

That is, if we consider a disk with a constant linear velocity, the linear velocity is V%l', the rack pitch is p, and the disk radial position of the main beam spot is r, then the following equation holds true.

From equations (1) and (2), The program area of the video area is at time to xQ.

Assuming that the radius starts from rQ, the position r at time t is given by equation (3).

When the distance between the tilt beam spot and the main beam spot is d, the disk radial position r' of the tilt beam spot is given by r + d. Therefore, since the temporal position t' of the tilt beam spot is the position of the position r' on the y-axis, v From equation (4), the temporal difference between the main beam spot and the tilt beam spot is , is proportional to the square of the separation pressure fid (d2). Here, p+ ■+ d
Since is constant, the time difference between the tilt beam spots is given as a constant value when there is no position in the y direction (when there is a deviation in the y direction, it becomes a function of r).

Here, since the absolute absolute time of the video area on the composite disc is included in the TOC information recorded in the lead-in area, the system controller 9 calculates by subtracting a constant value (2π/pV) d2 from the absolute absolute time. By doing this, it is possible to easily determine the position just before the tilt beam spot enters the mirror surface of the outer periphery of the disk. In the video area, the servo effective range S is from the start of the lead-in area to the immediately preceding position.

Therefore, in the video area, the system controller 9 controls the servo switch 71 of the tilt servo device 7 during the period from the time when it is detected that the main beam spot has arrived at the video area based on the position information of the position detector 11 to the above-mentioned immediately preceding position. By turning it on, tilt servo can be performed over the entire servo effective range.

In the above embodiment, a light beam dedicated to the tilt servo is used and the tilt servo device is configured such that the tilt beam spot is separated from the main beam spot by a predetermined distance d.
As shown in Publication No. 16719, etc., it is also applicable to a tilt servo device having a configuration in which the main beam is also used as a tilt beam, and according to such a servo device, the main beam spot becomes the tilt beam spot. , the servo effective range is the entire video area, and tilt servo can be performed over the entire video area,
More effective.

As described in detail, the tilt servo device according to the present invention operates the tilt servo only in the redo-in area when playing the CD area and over the entire servo effective range when playing the video area. Since the configuration is configured to perform this, it is possible to reduce residual tilt errors in both the CD area and the video area, and crosstalk can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an example of an optical information recording disk reproducing device equipped with a tilt servo device according to the present invention, and FIG. 2 is a configuration diagram showing an example of a tilt servo mechanism.
FIG. 3 is a block diagram showing an embodiment of the tilt servo device according to the present invention, FIG. 4 is a diagram showing the positional relationship between the main beam spot and the tilt beam spot on the disk, and FIG. 5 is a diagram showing the recording area of the composite disk. It is a diagram showing classification. Explanation of symbols of main parts 1...Composite disc 3...Optical pickup 5...Video information demodulation system 6...Digital information demodulation system 7... ...Tilt servo device 11...Position detector 13...Objective lens 17...Tilt mechanism 18...
・Tilt sensor different 2 flashes 312]

Claims (1)

[Claims] A tilt servo device that irradiates a tilt servo light beam onto an information recording surface of an information recording disk and controls the optical axis of the information detection light beam to be perpendicular to the information recording surface based on the reflected light. , when reproducing a disc having a first area where a predetermined digital signal is recorded and a second area where a frequency modulated video signal and a predetermined digital signal are multiplex recorded, the information detection light beam a detecting means for detecting which of the first and second areas the spot is located; and a detecting means for detecting in which of the first and second areas the spot is located; 1. A tilt servo device comprising: control means for performing tilt servo over the entire servo effective range when reproducing the region.